Islamic State (IS) group fighters raised their flags over towns and villages in the southern Syrian province of Daraa for the first time following fierce battles on Monday morning, witnesses told Middle East Eye.

Clashes broke out in countryside west of Daraa late last week between IS fighters and members of the armed Syrian opposition, the al-Qaeda affiliate the Nusra Front, and Ahrar al-Sham.

On Monday morning, the Yarmouk Martyrs brigade and the Muthanna Islamic movement - both of which are accused of being IS affiliates - took over the villages of Tseel and Adawan following fierce fighting.

Eyewitnesses from the area reported that for the first time, the fighters of IS had raised their black and white banners following their advance.

Locals in Tseel told MEE that IS fighters had executed a number of residents there, and had used mosque loudspeakers to call on the Syrian opposition to surrender their weapons and turn themselves in, or pledge allegiance to them.

The fierce clashes in the area resulted in the death on Monday of Abu Salah al-Masalma, Nusra's general military commander in Daraa.

Abu Salah al-Masalma, the general commander of Nusra in Daraa

On Sunday night, a Nusra fighter detonated a suicide bomb at a checkpoint controlled by Syrian opposition forces to the west of Daraa, killing and injuring a number of enemy fighters.

The Yarmouk Martyrs brigade, which has been accused of being affiliated to IS for over a year, now has full control of the Wadi Yarmouk basin in the western countryside.

The basin is a key strategic site that lies close to the border with Israel via the Golan Heights and Jordan, and is comprised of about 10 villages and towns.

IS fighters managed to besiege Nusra and Ahrar al-Sham in the villages of Sahem al-Jolan and Heit al-Latin, which has been a staging ground for military strikes against IS in the countryside west of Daraa.

Major reinforcements from Syrian opposition armed groups and Nusra arrived after noon from the eastern countryside of Daraa in an attempt to force IS fighters back and prevent them from further incursions in the area.